If a farmer finds a dead cow in the pasture, it could be a candidate for Canada’s BSE surveillance program.
While the 2004 national target of 8,000 tests has been exceeded, the Canadian Food Inspection Agency wants producers to continue submitting potential cases. By the end of October, 9,476 cases had been tested and all were negative.
However, confusion persists as to how producers should supply proper samples for testing, said Darcy Undseth, CFIA veterinary program specialist overseeing the BSE program in the four western provinces.
The target population is “four D” animals: the downers, diseased, dying and dead older than 30 months.
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Before BSE was discovered in Canada, these animals would likely have gone to slaughter or rendering, where inspectors would set them aside for testing.
With a slaughter system working at capacity on younger animals, and renderers charging for dead stock pickup, these animals no longer come through the usual channels.
“We have pushed these out of the federal slaughter system and somewhat out of the provincial slaughter system because we don’t have the capacity anymore. We no longer have somebody who has been given a set of instructions on what hits the four Ds,” said Undseth.
Investigators have also found people were not sure who to contact about testing, while others avoided reporting animals for fear of being singled out if they own a BSE-positive animal.
If a producer has an animal he believes falls into one of the target groups, he should call his veterinarian or the nearest CFIA office.
“BSE has enough vague signs that we don’t want to rule out any that might be worthwhile sampling, but we also have to make sure that we don’t just take anything,” Undseth said.
Testing healthy animals undermines the validity of the results when the chances of finding BSE are greater in the diseased and dying.
The first category of interest is when an animal dies unexpectedly.
Depending on weather conditions, brain tissue is still retrievable from dead animals. If it has been hot, the brain may have disintegrated, but in winter it can freeze and still be tested some time after death. The sample is retrieved from the brain stem found at the back of the skull where the neck joins the head and the point where the spinal cord goes into the brain.
The next category is the downer, which means an animal that is unable to get up, remain standing or walk.
BSE-infected animals tend to spook, jump over small objects or shadows on the ground, or splay their legs. This could make them fall causing leg injuries. So a downer animal could have had an accident or may have BSE weakening its nervous system.
Cows can become paralyzed after giving birth. For example, the case in Washington state last Dec. 23 involved a downer dairy cow.
“They thought it was a calving injury that knocked it down. Maybe it was and maybe it wasn’t, but it turned out to be BSE positive,” Undseth said.
A third category is the diseased or distressed. The animal may not walk properly, seems to be hypersensitive to touch, light or noise and shows a change in behaviour, carrying its head abnormally. It may also spook easily and be more likely to attack.
Cancer eye could cause blindness and the cow may mimic some of the BSE behaviour of shyness and head tossing. Severe lump jaw could see abnormal head positions and sensitivity around the head. Vets will examine cattle with extensive forms of these diseases to rule out BSE.
Carcasses awaiting test results will get a unique white tag that identifies it as a “BSE-sampled carcass.” Producers must hold carcasses until they are notified of a negative result. If it is positive, CFIA disposes of it.
The CFIA has set aside $4.1 million between now and December 2005 to encourage people to submit animals and offset producers’ veterinary and carcass disposal costs.
Dead stock collectors, renderers and veterinarians across Canada are also eligible for reimbursement of costs related to the sampling, tracing and holding of carcasses being tested.
